Fu Huhui, Liu Caiping, Peng Pengfei, Jiang Feilong, Liu Yongsheng, Hong Maochun
State Key Laboratory of Structural Chemistry Fujian Institute of Research on the Structure of Matter Chinese Academy of Sciences Fuzhou Fujian 350002 China.
Adv Sci (Weinh). 2020 Jun 11;7(14):2000731. doi: 10.1002/advs.202000731. eCollection 2020 Jul.
Trivalent lanthanide (Ln)-doped hollow upconversion nanocrystals (UCNCs) usually exhibit unique optical performance that cannot be realized in their solid counterparts, and thus have been receiving tremendous interest from their fundamentals to diverse applications. However, all currently available Ln-doped UCNCs are solid in appearance, the preparation of hollow UCNCs remains nearly untouched hitherto. Herein, a class of UCNCs based on Yb/Er-doped tetralithium zirconium octafluoride (LiZrF:Yb/Er) featuring 2D layered crystal lattice is reported, which makes the fabrication of hollow UCNCs with a peasecod-like shape possible after Ln doping. By employing the first-principle calculations, the unique peasecod-like hollow nanoarchitecture primarily associated with the hetero-valence Yb/Er doping into the 2D layered crystal lattice of LiZrF matrix is revealed. Benefiting from this hollow nanoarchitecture, the resulting LiZrF:Yb/Er UCNCs exhibit an abnormal green upconversion luminescence in terms of the population ratio between two thermally coupled states (H and S) of Er relative to their solid LiZrF:Yb/Er counterparts, thereby allowing to prepare the first family of hollow Ln-doped UCNCs as supersensitive luminescent nanothermometer with almost the widest temperature sensing range (123-800 K). These findings described here unambiguously pave a new way to fabricate hollow Ln-doped UCNCs for numerous applications.
三价镧系（Ln）掺杂的中空上转换纳米晶体（UCNCs）通常表现出独特的光学性能，这是其固态对应物所无法实现的，因此从基础研究到各种应用都受到了极大的关注。然而，目前所有可用的Ln掺杂UCNCs外观均为固态，迄今为止，中空UCNCs的制备几乎未被涉及。在此，报道了一类基于二维层状晶格的Yb/Er掺杂八氟锆酸四锂（LiZrF:Yb/Er）的UCNCs，这使得在Ln掺杂后制备豌豆荚状中空UCNCs成为可能。通过第一性原理计算，揭示了独特的豌豆荚状中空纳米结构主要与Yb/Er异价掺杂到LiZrF基体的二维层状晶格中有关。受益于这种中空纳米结构，所得的LiZrF:Yb/Er UCNCs相对于其固态LiZrF:Yb/Er对应物，在Er的两个热耦合态（H和S）之间的布居比方面表现出异常的绿色上转换发光，从而能够制备出第一类中空Ln掺杂UCNCs作为超灵敏发光纳米温度计，其温度传感范围几乎是最宽的（123 - 800 K）。这里描述的这些发现明确地为制备用于众多应用的中空Ln掺杂UCNCs开辟了一条新途径。
